In a conventional oscillating sprinkler, water entering the sprinkler drives a turbine which operates through a gear reduction system to drive a crank arm that is connected to the sprinkler tube. Rotation of the crank arm will thus oscillate the sprinkler tube through a given arc to move the spray pattern over the lawn. With a crank-type action, the velocity of the oscillation is greatest at the midpoint of the oscillating stroke and the velocity is at a minimum at the end portions of the stroke where the crank arm is at dead center position. Because of the variation in velocity, the discharge of water is not uniform throughout the oscillating stroke and a greater volume of water will be discharged at the end portions of the stroke which can result in "puddling" or overwatering.
In an attempt to provide a more uniform velocity throughout the entire area of oscillation, attempts have been made to incorporate a cam mechanism with the crank arm to reduce the velocity during the midportion of the oscillating stroke.
It is also desirable to be able to vary the magnitude or arc of the oscillating stroke of the sprinkler tube to accommodate different watering conditions. Similarly, it is advantageous to be able to shift the spray pattern to one side or the other of the axis of the sprinkler tube to direct the spray pattern to desired areas.